The present invention relates to the froth flotation of mineral ores and more particularly to unique promoters useful in the anionic circuit of froth flotation of phosphate and other mineral ores.
It is common practice in froth flotation to utilize a chemical collector which is selectively adsorbed on the surface of the particles to be collected in order to enhance the concentration of such particles in one phase (usually the froth phase) while leaving remaining particles in the other phase (usually the aqueous phase). For example, phosphate ores have been beneficiated traditionally by employment of a double flotation process wherein the phosphate sands are screened to remove coarse phosphate pebbles (usually larger than about 1.15 mm) and then attrition scrubbed and classified to remove fine clay minerals referred to as slimes in order to prepare the sands for admission to the first stage of the flotation process. In the first flotation stage (so-called rougher flotation) the ore, normally containing 10-30% bone phosphate of lime (BPL), is upgraded to about 40-65% BPL by utilization of crude tall oil carboxylic acid collectors, typically derived as a by-product from the paper industry. The resulting phosphate concentrate from the anionic flotation circuit typically is an unsaleable product because the silica or acid insoluble content is too high, normally ranging from about 8-40%. to reduce the insoluble content to about 5% or less, the concentrate from the first or anionic flotation stage is acid scrubbed, eg. with sulfuric acid, to desorb the carboxylic acid collectors and again deslimed to remove both slimes and the chemical collectors. The ore pulp then is neutralized to approximately pH 7 with, for example, caustic soda or ammonium hydroxide, and sent to a secondary (or cleaner) flotation stage wherein cationic collectors are used to upgrade further the proportion of BPL by reverse flotation of the silica impurity.
The tall oil fatty acid collectors and extender fuel oils used as reagents in the anionic circuit or rougher flotation of phosphatic particles are effective in the flotation of coarse sized ore particles greater than about 35 mesh (Typer standard sieve series); however, the foam bearing such coarse phosphate ore particles is unstable which makes the rougher flotation recovery yield below 80% on the average. A further problem encountered in the rougher flotation is that the fatty acid collectors are known to form micellar structures at the relatively high concentrations that are used in the phosphate flotation process. This phenomena hinders the absorption of the collectors on the solid phosphatic particles which is deleterious to the process.
Heretofore, amine oxides have proven to be highly effective promoters in the froth flotation of sylvite from sylvinite ores wherein cationic amine collectors are used, as disclosed in applicant's commonly assigned co-pending application Ser. No. 066,637, filed on Aug. 15, 1979. The present invention is based upon the unexpected and startling discovery that such amine oxides and other promoters are highly effective in promoting flotation of ores in anionic systems.